The use of high-power, fiber-coupled lasers continues to gain popularity for a variety of applications, such as materials processing, cutting, welding, and/or additive manufacturing. These lasers include, for example, fiber lasers, disk lasers, diode lasers, diode-pumped solid state lasers, and lamp-pumped solid state lasers. In these systems, optical power is delivered from the laser to a work piece via an optical fiber.
Various fiber-coupled laser materials processing tasks require different beam characteristics (e.g., spatial profiles and/or divergence profiles). For example, cutting thick metal and welding generally require a larger spot size than cutting thin metal. Ideally, the laser beam properties would be adjustable to enable optimized processing for these different tasks. Conventionally, users have two choices: (1) employ a laser system with fixed beam characteristics that can be used for different tasks but is not optimal for most of them (i.e., a compromise between performance and flexibility); or (2) purchase a laser system or accessories that offer variable beam characteristics but that add significant cost, size, weight, complexity, and perhaps performance degradation (e.g., optical loss or reduced speed due to delays involved while varying beam characteristics) or reliability degradation (e.g., reduced robustness or up-time). Currently available laser systems capable of varying beam characteristics typically require the use of free-space optics or other complex and expensive add-on mechanisms (e.g., zoom lenses, mirrors, translatable or motorized lenses, combiners, etc.) in order to vary beam characteristics. No solution appears to exist which provides the desired adjustability in beam characteristics that minimizes or eliminates reliance on the use of free-space optics or other extra components that add significant penalties in terms of cost, complexity, performance, and/or reliability. What is needed is an in-fiber apparatus for providing varying beam characteristics that does not require or minimizes the use of free-space optics and that can avoid significant cost, complexity, performance tradeoffs, and/or reliability degradation.
Additive manufacturing systems typically suffer from very steep spatial temperature gradients, which can cause extremely fast cooling rates after the material (e.g., metal) is melted by a fusing laser beam. These cooling rates and temperature gradients can cause large stresses to be trapped in the cooled material. The industry needs an effective way to slow the rate of cooling in the area surrounding the fusing laser beam.